1. Field of the Invention
The present invention relates to a method of forming an organic light-emitting display, and more particularly, to a method of forming an organic light-emitting display having a black matrix.
2. Description of the Related Art
With a rapid development of monitor types, novelty and colorful monitors with high resolution, e.g., liquid crystal displays (LCDs), are indispensable components used in various electronic products such as monitors for notebook computers, personal digital assistants (PDA), digital cameras, and projectors. The demand for the novelty and colorful monitors has increased tremendously.
Liquid crystal display (LCD) monitors control pixel luminance by adjusting voltage drop applied on a liquid crystal layer of the liquid crystal display. Differing from liquid crystal displays (LCDs), Organic Light Emitting Displays (OLEDs) determine the pixel luminance by adjusting forward bias current flowing through an LED. With self-lighting technique without requiring additional light source, OLEDs provide faster response time period than LCDs. In addition, OLEDs have the advantages of better contrast and wider visual angle. More important, OLEDs are capable of being manufactured by existing TFT-LCD process. The commonly used OLEDs utilize a low-temperature polysilicon thin film transistor (LTPS TFT) substrate or amorphous silicon (a-Si) substrate.
Please refer to FIG. 1, which shows a structure of a thin film transistor applied in an organic light emitting displays (OLEDs) according to the prior art. In prior art, for forming an Organic Light Emitting Display (OLED) 100, a black matrix 101 with a predetermined size is formed on a glass substrate 102. Next, depositing a buffer layer 104 and an amorphous thin film (not shown) over the black matrix 101 and the glass substrate 102; the amorphous thin film is recrystallized as a poly crystalline thin film by using excimer laser annealing (ELA) process. Furthermore, etching the poly crystalline thin film to form a pattern named as the semiconductor layer 106 is performed by using a first photo-etching-process (PEP). Afterward, a gate insulator 108 is deposited on the semiconductor layer 106 and the buffer layer 104.
Following this procedure, a gate metal 110 is formed using a metal-depositing process and a second PEP. Then, a source 103 and a drain 105 are formed by performing a Boron ion-implanting process for the semiconductor layer 106 using the gate metal 110 as a self-alignment mask. An inter-layer dielectric (ILD) 112 is deposited on the gate metal 110 and the gate insulator 108, and a third PEP is performed to remove a portion of the ILD 112 and the gate insulator 108 on source 103 and drain 105 to generate via holes 115. Next, performing a metal-depositing process and a fourth PEP to generate metal layers 114 (i.e. signal line and drain metal) which covers the via holes 115 and connecting to the source 103 and the drain 105. Then, a planarization layer 116 is deposited on the metal layer 114 and the ILD 112. And a fifth PEP is performed to remove a portion of the planarization layer 116 on the metal layer 114 connecting to the drain 105. After that, an Indium Tin Oxide (ITO) layer, serving as transparent electric conductivity film, is formed on the planarization layer 116. Then, a display electrode 118 is generated by using the sixth PEP. Finally, a light-emitting layer 120 and a cathode metal layer 122 can be sequentially performed to complete fabrication of the OLED 100.
In general, a pixel has a light-passing region 130 and a non-light-passing region 132 including the black matrix 101. The use of the black matrix 101 is to block light, thereby enhancing chromatic contrast and facilitating photo efficiency of a polarizer. Traditionally, the black matrix 101 fabricated at the bottom of the OLED 100, is a metal film having advantages of easy etching and well light-blocking. As shown in FIG. 2, the positions of the black matrix 101 relative to other layers of a thin film transistor before and after a heating process according to the prior art. In LTPS processes, especially the recrystallization process, high temperature may make the glass substrate shrink, resulting in a misalignment of the black matrix pattern with the other layer of TFT patterns which are formed after the black matrix. The use of a costly non-anneal glass is a resolution, however, cost of the whole OLED may rise as a result of using non-anneal glass.